The invention relates to a method for braking or stopping an electromotor which can be driven by a direct current, particularly a brushless direct current motor, in the case of a defect of the electromotor or the units connected to the latter.
The invention also relates to an electrical drive for a superposition steering for a vehicle or for an electromechanical brake (EMB), which presents an electromotor which can be driven by a direct current motor, particularly a brushless direct current motor, an electronic control and regulation unit, and a power electronic unit for controlling the electromotor.
The term “superposition steering” denotes all the steering types where a steering angle which has been set by the driver or a set steering moment can receive as a superposition an additional angle or an additional moment, particularly to increase the steering stability at the time of the steering angle superposition and to provide driver assistance, for example, for lane steering, at the time of the moment superposition.
The term “electromechanical brake” denotes all the brake installations in which a brake force is generated with an electromechanical actuator, particularly an electromotor with a connected gearing. The brake force is transmitted via a brake friction coating to a brake disk or a brake drum, to decelerate the vehicle.
The invention also relates to a computer program.
A controlled and reliable braking or stopping of an electromotor is required in many application cases. Particularly for applications that are critical for safety, where the electromotor represents an actuator for a safety-critical function, such as, for example, in the gearing of a steering system for a vehicle or for an electromechanical brake (EMB), a reliable error acquisition strategy is absolutely necessary.
Brushless electromotors or electronically commutated electromotors therefore are becoming increasingly important. They replace particularly electromotors with brushes in such industrial applications as actuators. The advantages compared to motors with brushes are primarily the lower maintenance efforts resulting from the absence of any commutator brushes that are subject to wear and the fact that the degree of effectiveness is in principle higher due to the absence of commutator losses caused by the brush transition resistances. In addition, in connection with “intelligent” electronic commutation devices, some functions can be implemented which are not possible with motors that have brushes, or which can be achieved only by considerable additional mechanical effort.
Because, in the case of brushless electromotors, the functions of mechanical, inherently substantially safer and more reliable components, in this case the commutator brushes of a commutator motor, are replaced by mechatronic components, appropriate measures must be used to reliably ensure the absence of breakdowns. Due to the relatively high complexity of the commutation electronics of brushless motors, the number of possible errors is relatively high.
In addition, in many safety-critical systems, the motor rpm or the motor position is measured with an rpm sensor or a position sensor, and used for the regulation of the system. In that case, a definite error processing strategy is required in case there is an error in the determination of the motor rpm or motor position.
An objective of the invention is to provide a method which allows the reliable braking or stopping of brushless direct current motors, in particular.
This problem is solved by a method and a device. The method is a method for braking an electromotor which can be driven by a direct current, such as a brushless direct current motor, in the case of the presence of an error of the electromotor or units connected therewith, characterized in that the presence of definite error states is verified, and the electromotor is braked, by carrying out, at least temporarily, a control of the electromotor which is adapted to the detected, definite error state, taking into account a maximum loading capacity of one of the electronic control units connected to the electromotor. The device is an electrical drive for a superposition steering for a motor vehicle or for an electromechanical brake (EMB), which presents an electromotor which can be operated with a direct current, such as a brushless direct current motor, an electronic control unit and a power electronics unit for controlling the electromotor, characterized in that the electronic control and unit presents a detector, for detecting an error of the electromotor and/or an electronic unit connected to the latter, and the electronic control unit presents a braking device, for braking the electromotor, when the detector detects an error, in which the braking device causes the power electronics, at least temporarily in at least one motor phase, to produce a short circuit as a function of the recognized, definite error state, taking into account a maximum loading capacity of the power electronics.